London has been battered by 50mph winds that have felled trees and caused travel chaos. Powerful gusts swept across the capital as the Met Office issued a yellow "be aware" weather alert for most of the country.

Elmgreen and Dragset could not have wished for a better morning to unveil their work.

In the crisp winter sunlight, it gleamed like a beacon from all sides of the square, instantly catching the eye, as works on the fourth plinth need to do.

The Scandinavian duo have been making works about art's role in public space for many years, so they were an ideal choice for the commission, and they have judged it perfectly.

What a curious sculpture it is. Defiantly unaggressive, it is an antidote to the imperial might celebrated elsewhere in the square. Instead of reflecting the irrepressible energy you might expect from a young boy at play, he is lost in reverie.

He stares into space, his mouth in a gentle smile, his right arm raised as if hailing the applause of a crowd rather than grasping a horsewhip. He recalls a cherub in a Renaissance painting.

Close up, the sculpture appears contemporary and historical. The boy harks from another era - what child today wears shorts and braces and rides a rocking horse? - and yet the horse appears to be bought from Ikea.

So it is partly a monument to the innocence of childhood. But there is, as always with Elmgreen and Dragset, an element of mischief. They have clearly borne the equestrian statue of George IV across the square in mind. George was lampooned by the caricaturists of his age, and in the light of the kitsch boy and his horse, his pomposity seems more ridiculous than ever.

This is Elmgreen and Dragset's prime achievement - puncturing the ludicrous trappings of power and vanity, and making the whimsical play of a child heroic.